Lecture 23

Question 1

How is predecidualization started?

Answer 1

In response to estrogen priming followed by actions of progesterone

Question 2

Endometrial differentiation doesn’t require what major factor?

Answer 2

Embryo

Question 3

Can predecidualization be induced?

Answer 3

In non-pregnant mice following mating or artificially induced decidualization (scartching cervix or infusing w/ progesterone-oil emulsion)

Question 4

When does pre-decidualization of the uterine stroma occur?

Answer 4

During the menstrual cycle and continues of in presence of embryo

Question 5

Why does decidualization occur?

Answer 5

• Lifespan of stromal cells is limited
• terminally differentiate to function as maternal part of the placenta
• Polyploidy might contribute to limited and specialized life (demise makes room for embryo, increased synthetic capacity -> increased transcription of genes)

Question 6

What does decidual tissue make up?

Answer 6

Maternal Placenta - site of contact and communication between conceptus and mother, limits invasion into uterus, produces luteotropic hormones

Question 7

What is artifical decidual tissue called?

Answer 7

Deciduoma

Question 8

Where does human stroma decidualization occur?

Answer 8

Mesometrial site of implantation

Question 9

How is stromal decidualization regulated?

Answer 9

Cyclin A,B/cdk1 during proliferation (mitosis)

Question 10

What is the next steps after mitosis in decidualization?

Answer 10

Increase in p21 and concomitant downregulation of cyclin D3 and cdk4

Question 11

Differentiation steps in decidualization:

Answer 11

1. Cyclin D3 and cdk4 have a role in stromal cell proliferation
2. Decidualization activates p21 which inhibits cdk4
3. Consequently, switch from cdk4 to cdk6/P21: progression through G phase and induction of endocycle

Question 12

What are the steps of early embryogenesis?

Answer 12

• 2nd wk, embryoblast differentiats into 2 germinal layers (epiblast and hypoblast)
• 3rd wk, epiblast undergoes differentiation fo the 3 embryonic germinal layers

Question 13

What does the epiblast form?

Answer 13

Tissue of the embryo as well as the amniotic epithelium

Question 14

What does the hypoblast form?

Answer 14

Umbilical vesicle

Question 15

What is the process of differentiation of the 3 embryonic germinal layers?

Answer 15

• Appearance of the primitive streak
• Laterally immigrating cells sink down to form deep layers of the meso blast and endoblast

Question 16

What is the primitive streak?

Answer 16

An accumulation of cells along the midline

Question 17

What are the three parts of the mesoblast?

Answer 17

paraxial, intermediate and lateral plate mesoderm (trilaminar germ disk)

Question 18

What is the process of differentiation of the early embryo?

Answer 18

Day 6 - Differentiation of the epiblast and hypoblast
Day 7.5 - Primordial amniotic cavity forms within epiblast, hypoblast growth and differentiates into parietal endoderm
Day 8 - Open roof of amniotic cavity formed, parietal endoderm development, extraembryonic mesoderm formation, beginning of yolk sac within parietal endoderm
Day 9 - More extraembryonic mesoderm, primary villi appears, Primary yolk sac completed
Day 14 - Primary yolk sac mostly degraded, secondary yolk sac formed, amniotic membrane differentiated, secondary villi developed, extraembryonic coelom developed, extraembryonic mesoderm differentiate into splanchnic mesoderm of yolk sac

Question 19

What are the functions of the placenta?

Answer 19

• Gas transfer (lungs)
• Excretory functions, water balance and pH regulation (kidney)
• Catabolic and resorptive functions (gut)
• Synthetic and secretory functions (endocrine)
• Metabolic and secretory functions (liver)
• Hematopoiesis of the bone marrow
• Heat transfer of the skin
• Immunological functions

Question 20

How are villi formation different in pigs vs. rodents/humans

Answer 20

diffuse structure vs. round cotyledons

Question 21

Difference in cotyledons in rodents vs humans

Answer 21

Single cotyledon (discoid placenta) vs. multiple cotyledons consolidated into a clust that resembles a single disc

Question 22

How is the structure of the trophoblast cell layer specific to rodents and primates?

Answer 22

Uterine epithelium (endometrium) is eroded away so that maternal blood comes into direct contact with the trophoblast surface (called hemochorial)

Question 23

How doe rodents trophoblast layer differ from humans?

Answer 23

trichorial (2 syncytial layers and a mononuclear cell type layer) vs. single syncytial layer + an underlying trophoblast stem cell layer

Question 24

Overview of implantation of human embryo:

Answer 24

• Trophoblast pentrates epithelium and invades the stroma
• Blastocyst sinks further into stroma and amnionic cavity appears
• Uterine tissue has grown over the implantation site (deciduoma response) and irregular spaces, blood sinusoids, have appeared in the syncytiotrophoblast

Question 25

What are integrins?

Answer 25

A family of more than 20 different transmembrane receptors w/ non-covalently associated alpha and beta heterodimers